1. Field of the Invention
The present invention generally relates to image processing apparatuses, such as copiers, printers, facsimile machines, and multifunctional peripherals. The present invention also relates to image processing methods.
2. Description of the Related Art
In a conventional image processing apparatus, such as a multifunctional peripheral, a processing region is ensured in a memory for each of multiple functions, such as copying, printing, and scanning functions individually. The individual function then performs data input/output control using its allocated processing region (see Japanese Laid-Open Patent Application No. 2003-341156, for example).
FIG. 1 shows a diagram illustrating how a memory in a conventional image processing apparatus is partitioned into plural processing regions for different functions. As shown, the memory is divided into four regions; namely, a copied image processing region; a printed image processing region; a scanner image processing region; and a program control region. Input and output of image data is controlled by using the individually allocated regions. In this way, contention among the individual functions for memory is prevented when the copy, print, and scanner functions are operated in a multiplex mode.
In a conventional color multifunctional peripheral, the copy function may be allocated about 300 MB, the printer function may be allocated about 150 MB, and the scanner function may be allocated about 280 MB of memory. When a memory size for program control is included, the total memory size may amount to as much as 1 GB, thus increasing cost.
Furthermore, image data handled by conventional information processing apparatuses is basically non-compressed raw data, where the image data is stored in a memory using a compression method specifically adapted for the particular image processing apparatus. Thus, the stored image data cannot be utilized except by the particular image processing apparatus, although the dedicated compression method may increase the image processing speed in the particular image processing apparatus.
A technology has been proposed whereby data is compressed using a standard compression technology, such as by JPEG or PDF, so that the stored data can be utilized by an externally connected personal computer or the like.
However, when image data read by a scanner is compressed at a low compression ratio, the data may not fit within a scanner image processing region that is provided in advance. As a result, the scanned image data may write over printed image data stored in an adjacent printed image processing region that is currently printing, resulting in an abnormal image (such as a destroyed image) in the printed result.
With reference to FIGS. 2A, 2B, and 2C, development of an abnormal image in a conventional image processing apparatus is described.
The figures show a memory that is partitioned into plural input image processing regions (VIN) and plural output image processing regions (VOUT), with a common region (C) placed between VIN and VOUT. When a manuscript is read, in order to save memory and increase image data transfer rate, image data that is read is compressed and transferred to the input image processing regions VIN. The compressed image data is then expanded and transferred to the output image processing regions VOUT.
With reference to FIG. 2A, when image data compressed at a standard compression ratio is stored in the input image processing regions VIN, image data 50 for page 1 that has been read with a scanner is compressed at the standard compression ratio and then transferred to the input image processing region VIN 51 where it is stored. The compressed image data is then expanded and restored, and then stored in the output image processing region VOUT 52. The restored image data is thereafter transferred to an engine portion for printing.
With reference to FIG. 2B, image data 53 for page 2 that has been read with the scanner is compressed at the standard compression ratio. The compressed image data is then transferred to the input image processing region VIN 54 where it is stored, avoiding the input image processing region VIN 51 where the previous image data is already stored. The input image processing region VIN 51 is avoided because it is possible that the previous image data is being expanded.
The compressed image data stored in the input image processing region VIN 54 is expanded and restored, and is then stored in the output image processing region VOUT 55, avoiding the output image processing region VOUT 52 where the previous image data is already stored (for the previous image data may be printing). The image data stored in the output image processing region VOUT 55 is then transferred to the engine portion for printing.
In this case, no abnormal image develops in the printed result.
However, as shown in FIG. 2C, if image data 53 for page 2 that has been read with the scanner is compressed at a compression ratio lower than the standard compression ratio, the image data 53 may overflow from the allocated input image processing region VIN 54 and enter the output image processing region VOUT 52 where the image data for page 1 is already stored, through the common region C, as indicated at 56. If this happens, an abnormal image develops during the printing of the print data for page 1.